Quantum information processing with an asymmetric error channel

Patent metadata

Field	Value
Publication number	US-2021125096-A1
Application number	US-201917253460-A
Country	US
Kind code	A1
Filing date	Jun 28, 2019
Priority date	Jun 29, 2018
Publication date	Apr 29, 2021
Grant date	—

Abstract

Techniques for performing quantum information processing using an asymmetric error channel are provided. According to some aspects, a quantum information processing includes a data qubit and an ancilla qubit, the ancilla qubit having an asymmetric error channel. The data qubit is coupled to the ancilla qubit. The ancilla qubit may be driven with a stabilizing microwave field to create the asymmetric error channel.

First claim

What is claimed is:

1 . A quantum information processing (QIP) system comprising:
a data qubit; and an ancilla qubit with an asymmetric error channel, the data qubit coupled to the ancilla qubit.

2 . The QIP system according to claim 1 , further comprising a measurement device configured to measure a property of the data qubit using the ancilla qubit.

3 . The QIP system according to claim 2 , wherein the measurement device is configured to measure the property of the data qubit using a quantum non-demolition measurement.

4 . The QIP system according to claim 3 , wherein the measurement device is configured to perform the quantum non-demolition measurement by:
causing the data qubit and the ancilla qubit to interact such that a state of the ancilla qubit is based on the property of the data qubit; and measuring the state of the ancilla qubit to determine the state of the data qubit.

5 . The QIP system according to claim 4 , wherein the measurement device is configured to suppress errors of a first type in the ancilla qubit by repeatedly performing the quantum non-demolition measurement.

6 . The QIP system according to claim 4 , wherein the measurement device comprises:
a readout cavity coupled to the ancilla qubit; and a cavity state detector configured to measure the state of the readout cavity.

7 . The QIP system according to claim 6 , wherein the measurement device is configured to measure the state of the ancilla qubit by:
causing the ancilla qubit and the readout cavity to interact such that a state of the readout cavity is based on the state of the ancilla qubit; measuring the state of the readout cavity to determine the state of the ancilla qubit.

8 . The QIP system according to claim 7 , wherein the cavity state detector comprises a phase-sensitive detector.

9 . The QIP system according to claim 8 , wherein the cavity state detector comprises a homodyne detector.

10 . The QIP system according to claim 2 , further comprising a microwave field source configured to cause the data qubit and the ancilla qubit to interact such that a z-component of a state of the ancilla qubit is based on the property of the data qubit.

11 . The QIP system according to claim 10 , wherein:
the ancilla qubit is an ancilla superconducting nonlinear asymmetric inductive element (SNAIL) with a resonance frequency; and the microwave field source is configured to apply a pump microwave field to the ancilla SNAIL at a pump frequency that is twice the resonance frequency of the SNAIL.

12 . The QIP system according to claim 11 , wherein the microwave field source is configured to:
apply at least one initialization microwave field to the ancilla qubit to initialize the ancilla qubit in a cat state along the x-axis of a Bloch sphere; and apply at least one drive microwave field to at least one of the data qubit and the ancilla qubit to create an interaction between the data qubit and the ancilla qubit.

13 . The QIP system according to claim 12 , wherein the microwave field source is configured to apply the at least one initialization microwave field to the ancilla qubit by adiabatically increasing an amplitude of a pump microwave field of the ancilla SNAIL, prepared in a vacuum state, from 0 to a pump amplitude value equal to K|α| 2 , where K is a strength of a Kerr nonlinearity of the ancilla SNAIL and a is a coherent state amplitude associated with the cat state.

14 . The QIP system according to claim 11 , wherein:
the data qubit is a transmon; the property of the data qubit is σ Z of the transmon; and the microwave field source is further configured to apply a drive microwave field to the transmon at the resonance frequency of the SNAIL and in phase with the pump microwave field to cause the data qubit and the ancilla qubit to interact such that a z-component of the state of the ancilla qubit is dependent on σ Z of the data qubit.

15 . The QIP system according to claim 11 , wherein:
the data qubit comprises a cat state in a linear oscillator; the property of the data qubit is a photon number parity of the cat state; and the microwave field source is further configured to apply a drive microwave field to the cat state in the linear oscillator at the resonance frequency of the SNAIL and in phase with the pump microwave field to cause the data qubit and the ancilla qubit to interact such that a z-component of the state of the ancilla qubit is dependent on the photon number parity of the data qubit.

16 . The QIP system according to claim 11 , wherein:
the data qubit comprises a Gottesman-Kitaev-Preskill (GKP) state in a linear oscillator; the property of the data qubit is a stabilizer of the GKP state; and the microwave field source is further configured to apply a drive microwave field to the ancilla SNAIL at a drive frequency equal to a difference between the resonance frequency of the SNAIL and a resonance frequency of the linear oscillator to cause the data qubit and the ancilla qubit to interact such that a z-component of the state of the ancilla qubit is dependent on a stabilizer of the GKP state of the data qubit.

17 . The QIP system according to claim 16 , wherein:
the microwave field source is configured to apply the drive microwave field to the GKP state in phase with the pump microwave signal; and the stabilizer of the GKP state of the data qubit is a S q stabilizer.

18 . The QIP system according to claim 16 , wherein:
the microwave field source is configured to apply the drive microwave field to the GKP state 90° out of phase with the pump microwave signal; and
the stabilizer of the GKP state of the data qubit is a S p stabilizer.

19 . The QIP system according to claim 11 , wherein:
the data qubit comprises a cat state in a data SNAIL; the property of the data qubit is σ z of the data SNAIL; and the microwave field source is further configured to apply, over an interaction time duration, a plurality of microwave fields to the data qubit and the ancilla qubit to cause the data qubit and the ancilla qubit to interact such that a z-component of the state of the ancilla qubit is dependent on σ z of the data qubit, wherein applying the plurality of microwave fields comprises:
applying a first microwave field with a frequency 2ω c to the ancilla qubit, wherein ω c is a resonance frequency of the ancilla qubit;
applying a second microwave field with a frequency 2ω t to the data qubit, wherein ω t is a resonance frequency of the data qubit;
applying a third microwave field with a frequency 2ω t −ω c to the data qubit;
applying a fourth microwave field with a frequency ω c to the ancilla qubit; and
applying a fifth microwave field with a frequency ω c to the data qubit.

20 . The QIP system according to claim 19 , wherein:
an amplitude of the first microwave field is constant over the interaction time duration; an amplitude of the second microwave field is time-varying over the interaction time duration; an amplitude of the third microwave field is time-varying over the interaction time duration; an amplitude of the fourth microwave field is time-varying over the interaction time duration; and an amplitude of the fifth microwave field is constant over the interaction time duration.

21 . The QIP system according to claim 20 , wherein:
a phase of the first microwave field decreases linearly over the interaction time duration; a phase of the second microwave field is constant at a first phase value during

Assignees

• Univ Yale

Inventors

• Puri Shruti
• Grimm Alexander
• Campagne-Lbarcq Philippe
• Girvin Steven M
• Devoret Michel

Classifications

• G06N10/40

  Physical realisations or architectures of quantum processors or components for manipulating qubits, e.g. qubit coupling or qubit control · CPC title

• G06N10/70 Primary

  Quantum error correction, detection or prevention, e.g. surface codes or magic state distillation · CPC title

• H04L1/04

  using frequency diversity · CPC title

• B82Y10/00

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G06N10/00 Primary

  Quantum computing, i.e. information processing based on quantum-mechanical phenomena · CPC title